The present invention relates to a boom lift in which a boom that can be raised, lowered, rotated, etc., is attached to a vehicle that is equipped with a travel apparatus and is capable of travel, and a work apparatus is provided to the distal end of this boom. More particularly, it relates to a device for controlling the travel and rotation of this boom lift.
Lifts generally comprise a boom that is hoistably and rotatably attached to a chassis, and a work platform on which a worker stands and which is oscillatably (able to rotate horizontally) attached to the distal end of the boom, and are designed such that the boom is raised, lowered, or rotated so as to move the work platform to the desired position by operating a boom control device provided to the work platform. With a lift such as this, the lifting work is usually performed after jacks provided to the chassis have been deployed downward so as to stabilize the chassis on the ground, but sometimes the work is performed while the chassis travels with the worker standing on the work platform.
When the chassis is thus made to travel while a worker is standing on the work platform, the worker on the work platform will be subjected to an impact (or shock) due to momentum, etc., if the platform is accelerated, decelerated, or stopped during its travel. This impact is exacerbated when the chassis is traveling with the boom deployed (raised, lowered, extended, or rotated). This impact tends to be particularly large when the flexural rigidity of the boom in the lateral direction is less than that in the longitudinal direction, and the boom is extended to the side or upward.
There are also times when the boom is rotationally operated while the chassis is traveling, in which case the work platform may move at an excessive speed, and there is the danger that a worker on the platform will be subjected to a large impact if the chassis should come to a sudden stop. Furthermore, travel in this state poses the danger that a large lateral momentum will be applied to the vehicle and travel stability will be lost.
It is an object of the present invention to provide a control device for a boom lift, designed such that a worker on the work platform will not be subjected to a large impact (momentum) if the chassis should accelerate or halt during its travel, regardless of the amount or position of boom deployment.
It is a further object of the present invention to provide a control device for a boom lift with which travel stability can be ensured for a vehicle so that a worker on the work apparatus (work platform) will not be subjected to a large impact (momentum) even if the boom is rotated while the vehicle is rotationally traveling.
The present invention is therefore a travel and rotation control device for a boom lift comprising a vehicle equipped with a travel apparatus and capable of travel, a boom that is attached to the vehicle and is at least hoistable and rotatable, and a work apparatus attached to the distal end of the boom, this control device comprising travel command means for outputting commands for the travel of the vehicle, boom rotation command means for outputting commands for rotationally operating the boom, position detection means for detecting the position of the work apparatus with respect to the vehicle, and control means for calculating the movement speed of the work apparatus at a position detected by the position detection means according to a travel command issued by the travel command means and/or a boom rotation command issued by the boom rotation command means, and controlling the travel of the vehicle and/or the rotation of the boom so that the movement speed of the work apparatus does not exceed a predetermined base speed.
With this constitution, the travel speed of the chassis is limited to a predetermined travel speed range according to the position of the work platform, so a worker on the work platform can be prevented from being subjected to a large impact when the chassis travel comes to a stop, regardless of the amount of boom deployment, by setting this travel speed range so as to be narrower (that is, so that the maximum obtainable speed will be lower) the greater is the amount of deployment of the boom. At the same time, the load acting on the boom distal end is also smaller, so decreased strength of the chassis and boom can also be prevented.
In the present invention, the position detection means can comprise rotation angle detection means for detecting the angle of rotation of the boom, in which case the base speed is preset according to the angle of rotation of the boom, and when the vehicle travels on the basis of travel commands issued by the travel command means, the control means reads the base speed according to the angle of rotation of the boom detected by the rotation angle detection means, and controls the speed of the vehicle so that the movement speed of the work apparatus does not exceed the base speed that has been read.
With this constitution, since the travel speed of the chassis is limited to a predetermined travel speed range according to the angle of rotation of the boom, a worker on the work platform can be prevented from being subjected to a large impact when the chassis travel comes to a stop, just as above, by setting this travel speed range so as to be narrower the greater is the amount of deployment of the boom. The load acting on the boom distal end is also smaller, so decreased strength of the chassis and boom can also be prevented. Fewer detectors are required with this constitution, so the structure can be simplified.
The present invention may also be constituted such that the position detection means consists of side clearance detection means for detecting the clearance to the side of the work apparatus with respect to the vehicle, the base speed is preset according to the side clearance, and when the vehicle travels on the basis of travel commands issued by the travel command means, the control means reads the base speed according to the side clearance of the work apparatus detected by the side clearance detection means, and controls the speed of the vehicle so that the movement speed of the work apparatus does not exceed the base speed that has been read.
The present invention may also be constituted such that the position detection means consists of upward clearance detection means for detecting the clearance above the work apparatus with respect to the vehicle, the base speed is preset according to the upward clearance, and when the vehicle travels on the basis of travel commands issued by the travel command means, the control means reads the base speed according to the upward clearance of the work apparatus detected by the side clearance detection means, and controls the speed of the vehicle so that the movement speed of the work apparatus does not exceed the base speed that has been read.
The present invention can also be constituted such that, when a command for the rotational travel of the vehicle issued by the travel command means is outputted simultaneously with a command for rotationally operating the boom issued by the boom rotation command means, the control means voids the command issued by the boom rotation command means and uses only the command issued by the travel command means to control the vehicle so that it travels rotationally.
The present invention may also be constituted such that, when a command for the rotational travel of the vehicle issued by the travel command means is outputted simultaneously with a command for rotationally operating the boom issued by the boom rotation command means, and the rotational direction of the vehicle is the same as the rotational direction of the boom, the control means voids the command issued by the boom rotation command means and uses only the command issued by the travel command means to control the vehicle so that it travels rotationally.
The present invention may also be constituted such that, when a command for the rotational travel of the vehicle issued by the travel command means is outputted simultaneously with a command for rotationally operating the boom issued by the boom rotation command means, the control means controls the travel of the vehicle and the rotational of the boom so that the movement speed of the work apparatus does not exceed a predetermined base speed.
By controlling operation as above, the movement speed of the work apparatus will never exceed the predetermined base speed, not only when there is a command causing the chassis to rotate suddenly, but even when there is a command for the rotation of the boom simultaneously with a command for the rotational travel of the chassis in the same direction, so the chassis can be kept from toppling and a worker on the work apparatus (work platform) will not be subjected to a large impact (excessive momentum), allowing the work to be carried out more stably.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.